Feedback regulation Used by controllers

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Feedback control 1. Flowchart 2. Initial conditions: Material 1: P=16 kg/cm2, T=-80°C, F=100 kgmol/hr; Composition: H2-0.01, CH4-0.68, C2H6-0.31 (mole fraction). Cooler E1: Heat load of 0.12 Mkcal/hr. Gas-liquid separation tank: Pressure and temperature are the same as those at the cooler’s outlet. Pressure reducing valve V1: Reduces pressure to 6 kg/cm2. Gas-liquid separation tank: Pressure and temperature are the same as those at the V1 outlet. 3. Results of flow calculations: Temperature at E1 outlet: –105.24°C. Flow rate of S4: 90.5 kgmol/hr. Flow rate of S7: 73.94 kgmol/hr. 4. Feedback control: Control requirement: By adjusting the heat load of cooler E1, the flow rate of material S7 should be made 60 kgmol/hr. 5. Analysis: This is a typical feedback control calculation. By using the calculated flow rate of S7, the heat load of the upstream heat exchanger is adjusted so that the final flow rate of S7 reaches 60 kgmol/h. 7. Definition A. The heat load of the heat exchanger is a control parameter; its value must be controlled to meet the control requirements ； B. The flow rate of the liquid phase S7 after throttling is the control target. 8. Key points for solving the problem: A. The values of the control parameters must remain fixed and cannot be changed arbitrarily. B. The values of the control targets cannot be fixed; they must be calculated automatically by the respective unit process. 9. Results of feedback control calculations: E1 heat load: 0.08928 Mklcal/hr; E1 outlet temperature: –100.23°C; S4 flow rate: 74.8 kgmol/hr; S7 flow rate: 60 kgmol/hr. The inp file contains the following information: $ Generated by PRO/II Keyword Generation System $ Generated on: Sun May 01 22:49:03 2011 TITLE DIMENSION SI, TEMP=C, PRES=KG/CM2, STDTEMP=0, STDPRES=1.03323 SEQUENCE SIMSCI CALCULATION RVPBASIS=APIN, TVP=37.778 COMPONENT DATA LIBID 1,H2/2,METHANE/3,ETHANE THERMODYNAMIC DATA METHOD SYSTEM=IDEAL, SET=IDEA01 METHOD SYSTEM=PR, SET=PR01, DEFAULT METHOD SYSTEM=SRK, SET=SRK01 STREAM DATA PROPERTY STREAM=S1, TEMPERATURE=-80, PRESSURE=16, PHASE=M, & RATE(M)=100, COMPOSITION(M)=1,0.01/2,0.68/3,0.31 UNIT OPERATIONS HX UID=E1 HOT FEED=S1, M=S2 OPER DUTY=0.50242 FLASH UID=F1 FEED S2 PRODUCT V=S3, L=S4 ISO TEMPERATURE=-112.29 VALVE UID=V1 FEED S4 PRODUCT M=S5 OPERATION PRESSURE=6 FLASH UID=F2 FEED S5 PRODUCT V=S6, L=S7 ISO TEMPERATURE=-126.77 CONTROLLER UID=CN1 SPEC STREAM=S7, RATE(KGM/H),TOTAL,WET, VALUE=60 VARY HX=E1, DUTY(KJ/HR) CPARAMETER IPRINT, NOSTOP END